High throughput printing systems, such as those used in high speed printers and color copiers, or large format devices put heavy demand on an ink delivery system. The printhead must operate at a very high frequency. At the same time, print quality expectations keep rising. In order to maintain high print quality, the printhead must be able to rapidly eject ink without causing large fluctuations in the printhead pleasure level.
One approach to this is to provide a pressure regulator integral to the printhead. The regulator receives ink at a first pressure and delivers ink to the printhead at a controlled second pressure. In order for this control to work, the first pressure must always be greater than the second pressure. Because of dynamic pressure drops, very high pixel rate printing requires that the first pressure be at a positive gauge pressure.
One example of an ink cartridge that can be pressurized is described in U.S. Pat. No. 4,568,954. Other references include U.S. Pat. Nos. 4,558,326; 4,604,633; 4,714,937; 4,977,143; Saito U.S. Pat. Nos. 4,422,084; and 4,342,041.
One problem with previous high throughput devices is predicting when the consumable will be exhausted. It is important that the system stop printing when the ink cartridge is nearly empty, with a small amount of stranded ink. Otherwise, dry firing and consequent printhead damage may occur. Printheads for such high throughput devices tend to be expensive. What is needed is an ink cartridge that offers pressurized ink and provides an accurate means of indicating the low ink condition.
To provide an ink container having all of these features is a challenge. As can be appreciated, such an ink container can become very complicated, making manufacture very difficult and expensive. What is need is a way of simplifying the construction and of providing all these features with a relatively simple and manufacturable design.